1. Field
Embodiments of the present invention relate to a nonvolatile semiconductor memory device.
2. Description of the Related Art
A resistance varying type memory using a variable resistance element as a memory cell is proposed as a technology achieving further miniaturization of the memory cell. Known as the variable resistance element are: a phase change element that changes its resistance value by a change between crystalline/amorphous states of a chalcogenide compound; a MRAM element that employs resistance change due to a tunnel magnetoresistive effect; a memory element of polymeric ferroelectric RAM (PFRAM) where the resistance element is formed by a conductive polymer; a ReRAM element that causes resistance change by an electric pulse application; and so on.
The variable resistance element is capable of electrically switching between at least two resistance values, for example, a high-resistance state and a low-resistance state. The variable resistance element is disposed at an intersection of a bit line and a word line that cross each other, and thereby configures a memory cell array. Moreover, in the case of a resistance varying type memory, it is effective to add a protective resistance film to the variable resistance element in order to suppress current flowing in the variable resistance element during a setting operation or a resetting operation.